There have been known control means and actuating means for measuring, driving, and controlling used for controlling plants and equipment, with which the measurement result is returned in the form of analog signal as shown in the following items (1) to (3).
(1) A sensor such as a transmitter for measurement, which is supplied with electric power and outputs measurement results of temperature, humidity, and pressure converting them into analog signals.
(2) A sensor such as a thermocouple and resistance thermometer bulb, which outputs measurement result as a change of voltage and electric resistance.
(3) A control actuator such as a servo valve which is supplied with electric power and controls valve opening from full open to full close in accordance with imputed voltage signals.
There have also been known control means which return measurement results in binary signals (digital signals) or driven by binary signals as shown in the following items (4) to (6).
(4) A control means having a contact for switching-on and -off upon detecting that pressure or temperature reaches a prescribed value and being utilized for detecting ambient conditions, the means being supplied with electric power.
(5) A control means such as a relay contact or ON/OFF switching means made of semiconductor, which actuates upon receiving a binary signal, i.e. ON/OFF signal.
(6) An actuator such as an electromagnetic valve, lamp, relay, small DC motor, etc., which is supplied or cut-off with electric power to be driven or stopped upon receiving an ON/OFF signal.
In such a measurement instrument or a driven device such as an actuator, an instruction side to send instruction to the plant and equipment is insulated from a side performing measurement or driving or controlling in the plant side (hereafter referred to as the plant side) depending on use for the purpose of preventing affections on the human body or evading affections of noise. This is generally done by adopting an insulation transformer as a transducer of the power source for supplying electric power or insulating a measurement signal sent from the plant side to instruction side from an instruction signal or control signal sent from the instruction side to the plant side by means of a photocoupler, insulation signal relay, insulation amplifier, insulation transformer, etc.
In recent years, there has been increased demand for soundness diagnosis to diagnose the state of signals in circuits in the field of instrumentation and measurement for the purpose of raising reliability by confirming soundness of output signals and circuit wiring, that is, confirming whether there is breaking of wire or short-circuit occurred in the circuits, and whether actuators for controlling and driving are operating as instructed.
FIGS. 18 to 27 show examples of conventional measuring means such as sensors, transmitter for measurement, etc., driven devices such as drive means and control means such as servo valves, relays, actuators including motors in block diagrams.
FIGS. 18 to 23 show cases where soundness diagnoses are not performed, whereas FIGS. 24 to 27 show cases where a circuit for performing soundness diagnosis is provided.
First, examples of conventional circuits not provided with soundness diagnosing circuit will be explained one by one.
FIG. 18 is a block diagram of a circuit in the case of the item (1), i.e. in the case of a sensor such as a transmitter for measurement, which is supplied with electric power and outputs measurement results of temperature, humidity, and pressure converting them into analog signals.
Electric power of 24 V, for example, is supplied to a transmitter for measurement 100, signal conversion circuit 108, and modulation circuit 109, from a power source circuit 101.
The power source circuit 101 consists of a pulse generating circuit 103 for converting electric power supplied from a power source 102 into pulse voltage, an insulation transformer 104 for changing the voltage of the pulse voltage from the pulse generating circuit 103 and insulates the plant side from instruction side, a rectifying circuit 105 for rectifying the pulse voltage transformed by the insulation transformer 104, and a constant-voltage circuit 106 for smoothing the rectified pulse voltage into a constant voltage.
The signal conversion circuit 108 and modulation circuit 109 are for inputting measurement results of temperature, humidity and pressure as AC signals to the insulation transformer 110 used for dividing the measurement transmitter 100 side from the instruction side. The measurement transmitter 100 can not input the measurement signals to the insulation transformer 110, because electric currents generated by the temperature, humidity and pressure sensors are currents varying in a range of about 4˜20 mA. Therefore, the measurement results obtained as electric currents are converted into voltage signals by the signal conversion circuit 108, and further converted into alternating voltage signals by the modulating circuit 109 to be inputted to the insulation transformer 110. Then, the output of the insulation transformer 100 is reconverted to a current or voltage signal 112 to be outputted outside as measurement results.
A broken line denoted by reference numeral 107 in FIG. 18 represents an insulation barrier insulating the measuring side (instruction side) from the measuring device side (plant side). In the following explanation, constituent components similar to those in FIG. 18 are denoted by the same reference numerals and detailed explanation is omitted.
FIG. 19 is a block diagram of a circuit in the case of the item (2), i.e. in the case of a sensor such as a thermocouple and resistance thermometer bulb, which outputs measurement result as a change in voltage and electric resistance.
The power source circuit 101 consists, similarly to the case of FIG. 18, of a power source 102, pulse generating circuit 103, insulation transformer 104, and rectifying circuit 105, constant-voltage circuit 106. Electric power is supplied to a signal conversion circuit 121 and modulation circuit 122. The voltage signals and resistance signals from thermocouples and resistance thermometer bulb are converted into voltage signals by the signal conversion circuit 121 and converted into AC signals by the modulation circuit 122, amplified by an insulation transformer 123 which is a signal insulating means to insulate the plant side from instruction side, then the output from the insulation transformer 123 is reconverted into current or voltage signals 125 by a demodulating circuit 124 to be outputted outside as measurement results.
FIG. 20 is a block diagram of a circuit in the case of the item (3), i.e. in the case of a control actuator 130 (hereafter referred to as an object) such as a servo valve which is supplied with electric power and controls valve opening from full open to full close in accordance with imputed voltage signals.
The power source circuit 101 consists, similarly to the case of FIG. 18 and FIG. 19, of a power source 102, pulse generating circuit 103, insulation transformer 104, and rectifying circuit 105, constant-voltage circuit 106.
A voltage signal 131 for driving the object 130 is converted into an AC signal by a modulation circuit 132, the AC signal is amplified by an insulation transformer 133 in which the AC signal is insulated between the plant side and instruction side, then demodulated by a demodulating circuit 134 which is supplied with electric power from the power source circuit 101, and converted by a signal conversion circuit 135 which is also supplied with electric power from the power source circuit 101 to be inputted to the object 130.
FIG. 21 is a block diagram of a circuit in the case of the item (4), i.e. in the case of a control means having a contact for switching-on and -off upon detecting that pressure or temperature reaches a prescribed value and being utilized for detecting ambient conditions, with electric power supplied to the control means. The power source circuit 101 for supplying electric power to drive contact 140 and 143 which outputs an ON-OFF signal consists, similarly to the case of FIG. 18, FIG. 19, and FIG. 20, of a power source 102, pulse generating circuit 103, insulation transformer 104, and rectifying circuit 105, constant-voltage circuit 106. Even in a case there are a plurality of contacts as this case, a single power source circuit 101 is provided generally for common use for the contacts in view of cost saving.
When the contact 140, 143 is switched on or off at the prescribed pressure or temperature, the signal is sent to a photocoupler 141, 144 which is used for insulating between the plant side and instruction side, a light emitting element of the photocoupler 141, 144 emits light when the contact 140, 143 is ON, a binary signal 142, 145 of ON/OFF is outputted from a light sensitive element of the photocoupler 141, 144. In this way, temperature or pressure of the plant side is transmitted to the instruction side or object to be controlled.
FIG. 22 is a block diagram of a circuit in the case of the item (5), i.e. in the case of a control means such as a relay contact or ON/OFF switching means made of semiconductor, which actuates upon receiving an ON/OFF signal.
A binary signal 153, 154 for switching-on or -off a contact 151, 152 is inputted to a photoMOS relay 155, 156 which is used for insulation similarly as in the case of FIG. 21, and the contact 151, 152 is driven similarly as in the case of FIG. 21. A broken line denoted by a reference numeral 157 indicates an insulation barrier for insulating the plant side from instruction side by the photoMOS relay 155, 156, and this insulation barrier also insulates signals sent to the contact 151, 152.
FIG. 23 is a block diagram of a circuit in the case of the item (6), i.e. in the case of an actuator 163 such as an electromagnetic valve, lamp, relay, small DC motor, etc. (hereafter referred to as an object depending on circumstances), which is supplied or cut-off with electric power to be driven or stopped upon receiving an ON/OFF signal. A drive voltage signal 160 is inputted to a signal insulation relay 161 for insulating the plant side from instruction side similarly as in the case of FIG. 22, and electric power supplied from a DC power source 162 provided separately is transmitted to the object 163 which is an actuator such as an electromagnetic valve, lamp, relay, small DC motor, etc. to drive it.
Measurement and control by the measuring means and drive means as mentioned in the items (1) to (6) used to control the plant and equipment are performed in this way. As can be seen from the explanation above, it is necessary to provide insulation power source using an insulation transformer, etc., and when sending signals from the instruction side to plant side and vice versa, an insulating means such as a photocoupler, signal insulation relay, insulation amplifier.
Next, cases where a circuit for performing soundness diagnosis is added to the circuits explained above will be explained. The soundness diagnosing circuit is provided to raise reliability by confirming soundness of output signals and circuit wiring, that is, confirming whether there is breaking of wire or short-circuit occurred in the circuits, and whether actuators for controlling and driving are operating as instructed.
In the circuits shown in FIG. 18 and FIG. 19, that is, in the case of the item (1), i.e. in the case a sensor such as a transmitter for measurement, which is supplied with electric power and outputs measurement results of temperature, humidity, and pressure converting them into analog signals, and in the case of the item (2),i.e. in the case a sensor such as a thermocouple and resistance thermometer bulb, which outputs measurement result as a change in voltage and electric resistance, soundness of a circuit can be judged to some extent from a condition that a measurement result is not inputted to the instruction side or a measurement result does change from a constant value.
However, in the cases of FIGS. 20 to 23, that is, in the case of the item (3), i.e. in the case of a control actuator such as a servo valve which is supplied with electric power and controls valve opening from full open to full close in accordance with imputed voltage signals, in the case of the item (4), i.e. in the case of a control means having a contact for switching-on and -off upon detecting that pressure or temperature reaches a prescribed value and being utilized for detecting ambient conditions, the means being supplied with electric power, in the case of the item (5), i.e. in the case of a control means such as a relay contact or ON/OFF switching means made of semiconductor, which actuates upon receiving an ON/OFF signal, and in the case of the item (6), i.e. in the case of an actuator such as an electromagnetic valve, lamp, relay, small DC motor, etc., which is supplied or cut-off with electric power to be driven or stopped upon receiving an ON/OFF signal, it is necessary to confirm whether the control means are working normally, in addition to whether there is breaking of wire or short-circuit occurred in the circuits, etc.
However, confirmation of whether the control means and actuators are working in accordance with instructions can not be implemented without providing some kind of composition for the purpose. FIGS. 24-27 show examples of block diagrams of circuits added with soundness diagnosing circuits in the cases of the items (3) to (6). The examples of FIGS. 24 to 27 correspond to those of FIGS. 20-23 respectively, similar constituent elements are denoted by the same reference numerals, and explanation of the components is omitted.
First, FIG. 24 is a block diagram of a circuit in the case of the item (3), i.e. in the case of a control actuator such as a servo valve (hereafter referred to as an object depending on circumstances) which is supplied with electric power and controls valve opening from full open to full close in accordance with imputed voltage signals as explained in FIG. 20. The power source circuit 101 consists, similarly to the case of FIG. 20, of a power source 102, pulse generating circuit 103, insulation transformer 104, and rectifying circuit 105, constant-voltage circuit 106. An actuator which is the object 130 to be driven is driven by the signal (similarly as in FIG. 20) obtained by converting the voltage signal 131 into an AC signal by the modulation circuit 132, amplifying the AC signal by the insulation transformer 133, demodulating by the demodulating circuit 134, and converting by the signal conversion circuit 135 into a voltage or current signal corresponding to the voltage signal 131.
A diagnosing circuit in this case is composed such that; it comprises a signal conversion circuit (for current) 136a and same (for voltage) 136b, which are supplied with electric power from the electric power circuit 101 and detect the current or voltage inputted from the signal conversion circuit 135 to the object 130, modulation circuits 137a and 137b for modulating the signals from the signal conversion circuit 136a and 136b into AC signals respectively so that they can be inputted to insulation transformers 138a and 138b respectively, and demodulation circuit 139a and 139b for demodulating the voltages transformed by the transformer 138a and 138b respectively; and diagnoses whether the circuit is operation as instructed, whether there is breaking of wire or short-circuit occurred in the circuits, etc. by detecting whether electric current is passing to the object 130, whether applied voltage is appropriated for the operation of the object, etc.
FIG. 25 is a block diagram of a circuit in the case of the item (4), i.e. in the case of a control means (hereafter referred to as a contact) having a contact for switching-on and -off upon detecting that pressure and temperature reaches a prescribed value and being utilized for detecting ambient conditions, the means being supplied with electric power, as explained in the case of FIG. 21.
The power source circuit 101 consists, similarly to the case of FIG. 21, of a power source 102, pulse generating circuit 103, insulation transformer 104, and rectifying circuit 105, constant-voltage circuit 106. Even in a case there are a plurality of contacts as this case, a single power source circuit 101 is provided generally for common use for the contacts in view of cost saving similarly to the case of FIG. 21.
Diagnosis is performed by a block 146, which is composed of a microcomputer, etc. such that condition of the contacts are perceived and evaluated in an analog fashion by means of an A/D conversion means and soundness of the circuit is judged by confirming the state of ON/OFF switch, existence of short-circuit and malfunction of the contacts, and breaking of wire or short-circuit in the circuit, etc. The result of the diagnosis is sent to a photocoupler 141 which is a means to insulate signals between the plant side and instruction side, and outputted from the photocoupler 141 as serial communication signals to be sent to a signal receiving part 147.
In this case, a common power source is utilized for a plurality of signals from point of view of cost saving, so when two or more contacts different largely in location are provided, difference in voltage occurs due to difference in voltage drop caused by difference of length of signal wires. Therefore, it is necessary principally to perform diagnosis contacts located near to one another. Because of common power source, the block 146 for diagnosing the soundness of the circuit performs evaluation of signals in an analog fashion in the plant side.
FIG. 26 is a block diagram of a circuit in the case of the item (5), i.e. in the case of a control means such as a relay contact or ON/OFF switching means made of semiconductor, which actuates upon receiving an ON/OFF signal (hereafter referred to as a contact). Though the power source circuit 101 is not used in the case of FIG. 22, a diagnosing circuit composed of a microcomputer, etc. is needed in this circuit of FIG. 26 to diagnose the state of contact, etc. similarly to the case of FIG. 25. In addition, when each of the contacts is insulated separately between the plant side and instruction side, an insulation power source is needed for each of the contacts separately to drive each diagnosing circuit.
Each of power source circuits is composed similarly as in the above examples, and when the number of contacts is two for example, they respectively consist of a power source 102a, 102b, a pulse generating circuit 103a, 103b, an insulation transformer 104a, 104b, rectifying circuit 105a, 105b, and a constant-voltage circuit 106a, 106b. 
A binary signals 153, 154 for switching on/off a contact 151, 152 is inputted to a photocoupler 155, 156 used for the purpose of insulation between the plant side and instruction side similarly to the case of FIG. 21, then sent by way of a monitoring circuit 158a, 158b for checking contact conditions of the contact signal and read over signal to the contact 151, 152 to drive it. The signal checked by the monitoring circuit 158a, 158b is outputted via a photocoupler 159a, 159b as a read over signal.
That is to say, in order to perform diagnosis of soundnedd of the circuit such as whether the photocouplers 155, 156, contacts 151, 152, etc, are working normally, whether there is no braking of wire and short-circuit, it is necessary to provide the monitoring circuits 158a, 158b and power source circuits 101a, 101b for driving the monitoring circuits. Therefore, actual example of use is limited to very special use.
FIG. 27 is a block diagram of a circuit in the case of the item (6), i.e. in the case of an actuator such as an electromagnetic valve, lamp, relay, small DC motor, etc. (hereafter referred to as an object depending on circumstances), which is supplied or cut off with electric power to be driven or stopped upon receiving an ON/OFF signal, as explained in the case of FIG. 23.
In the case of FIG. 23, the DC power source 162 for driving the object 163 which is an actuator such as an electromagnetic valve, lamp, relay, small DC motor, etc., is provided, and a drive voltage signal 160 is supplied to the object 130 via the signal insulation relay 161. This is the same also in the case of FIG. 27.
In the case of FIG. 27, there are provided a signal conversion circuit 164 for detecting the current of the actuator 163 and convert it into a voltage signal, a modulating circuit 165 for modulating the voltage signal into an AC signal, an insulation transformer 166, a demodulating circuit 167 for demodulating voltage signal into current signal, and a power source circuit 101 for driving a signal conversion circuit 164 and modulating circuit 165, the circuit 101 consisting of the power source 102, pulse generating circuit 103 insulation transformer 104, rectifying circuit 105, and constant-voltage circuit 106 similarly in the case of FIG. 25, for the purpose of diagnosing soundness of the circuit such as whether the object, i.e. actuator 160 is operating as instructed, and whether there is no breaking of wire or short-circuit, etc.
The drive voltage signal 160 is inputted to the signal insulating relay 161 for signal insulation, and the power form the DC power source 162 is sent to the object such as a electromagnetic calve, lamp, relay, small DC motor via the signal insulating relay 161 to drive the object similarly to the case of FIG. 23. The current sent from the DC power source 162 via the signal insulation relay 161 is detected by the signal conversion circuit 164 for detecting current, the detected current is converted into an AC voltage signal by the modulating circuit 165 to be inputted to the insulation transformer 166, then converted into a current signal by the demodulating circuit 167 to be outputted as a read over current signal 168.
As mentioned above, in the case of FIG. 27, additional circuits such as signal conversion circuit 164, modulating circuit 165, insulation transformer 166, and demodulating circuit 167, and the power source circuit 101 to drive them are needed. Therefore, manufacturing cost increases very much and actual example of use is limited to very special use.
As has been mentioned, in the case of conventional circuit, even if soundness diagnosis of the circuit is not performed, an insulation power source having a constant-voltage circuit is needed to perform accurate measurement and drive excluding the cases of the item (5), i.e. the case of a control means such as a relay contact or ON/OFF switching means made of semiconductor, which actuates upon receiving an ON/OFF signal, and the case of the item (6), i.e. the case of an actuator for controlling an electromagnetic valve, lamp, relay, small DC motor, etc., which is supplied or cut-off with electric power to be driven or stopped upon receiving ON/OFF signal.
In the case of the item (1), i.e. in the case of a sensor such as a transmitter for measurement, which is supplied with electric power and outputs measurement results of temperature, humidity, and pressure converting them into analog signals, in the case of the item (2), i.e. in the case of a sensor such as a thermocouple and resistance thermometer bulb, and in the case of the item (3), i.e. in the case of a control actuator such as a servo valve which is supplied with electric power and controls valve opening from full open to full close in accordance with imputed voltage signals, a signal conversion circuit, modulating circuit, insulation transformer and demodulating circuit are necessary to be provided.
In the case the item (4), i.e. in the case of a control means having a contact for switching-on and -off upon detecting that pressure or temperature reaches a prescribed value and being utilized for detecting ambient conditions, the means being supplied with electric power as shown in FIG. 21, a single common power source is provided for a plurality of signals from point of view of cost saving even when it is desired to receive signals from a plurality of contacts in a state they are insulated from one another. Therefore, when two or more contacts different in location largely are provided, difference in voltage occurs due to difference in voltage drop caused by difference of length of signal wires. Therefore, it has been necessary principally to perform diagnosis of contacts located near to one another.
Furthermore, when incorporating a soundness diagnosing function in a circuit, there occur problems as follows:
(A) It is necessary to provide a power source and circuit for performing soundness diagnosis in addition to a transfer circuit for transferring signals for commanding measurement, drive, or control, and signals for telling measurement result, which causes increase in the number of parts, complexity of the circuitry, and manufacturing cost.
(B) In a case there are a plurality of contacts and they are insulated from one anther, when a soundness diagnosing circuit is provided for each of the contacts and the contacts are located distantly from one another, it is necessary to provide an expensive insulation power source for each soundness diagnosing circuit, causing further increase of manufacturing cost.
(C) To cope with this, when a single expensive insulation power source is provided for common use for each of the contacts, and when the contacts are located distantly from one another, difference in voltage occurs due to difference in voltage drop caused by difference of length of signal wires. Therefore, it has been necessary principally to perform diagnosis of contacts located near to one another.
(D) As the power source for driving an electromagnetic valve, etc. must be large in capacity as compared with that used for instrumentation and measurement, the former must be provided separately.
(E) When transmitting DC signals via a insulation transformer or insulation amplifier, the DC signals must be modulated once into AC signals, and then demodulated into DC signals.
As to the art for detect braking of wire, there are disclosed for example in patent literature 1 (Japanese Laid-Open Patent Application No. 2006-023105) a method of detecting breaking of wire by applying a pulse signal to the wire, and comparing the current wave shape measured with the reference current wave shape to judge the presence or absence of breaking of wire from difference in both the wave shapes, and in patent literature 2 (Japanese Laid-Open Patent Application No. 2004-198302) a circuit for detecting breaking of wire by applying a pulse signal for checking via an impedance component to the signal wire for detecting breaking of wire, and comparing the signal obtained from the signal wire with the pulse signal for checking to judge the presence or absence of breaking of wire.
A to diagnosis of electric circuits, there is disclosed for example in patent literature 3 (Japanese Laid-Open Patent Application No. 8-005708) a method of diagnosing electric circuits and diagnosing device used for the method. With which conditions of electric apparatuses are diagnosed for the purpose of improving efficiency of diagnosis operation by facilitating measurement record management and further decreasing occurrence of man-caused errors, by reading out information written and stored in a nonvolatile memory concerning measurement results of characteristics or things concerning measurement of the electric apparatuses, and comparing the read-out information with the information of-the-moment concerning measurement results of characteristics or things concerning measurement of the electric apparatuses.
However, with the art taught in the patent literature 1 and 2, means for applying pulse signals and a memory for memorizing reference current wave shape are needed, and with the electric circuit diagnosing device disclosed in the patent literature 3, a memory memorized information concerning measurement results of characteristics or things concerning measurement of the electric apparatuses is needed, and further a means for measuring characteristics of the circuit and a means for comparing the measurement result with the reference data, resulting in complicated composition. Therefore, problems cited in the items (A)˜(B) can not be solved by these art.